Purification, characterization and biotechnological application of an alkaline β-keratinase produced by Bacillus subtilis RM-01 in solid-state fermentation using chicken-feather as substrate

We report the application of response surface methodology (RSM) for optimization of the media composition for β-keratinase production by a feather degrading Bacillus subtilis strain RM-01 in solid-state fermentation using chicken-feather as substrate. The optimized culture conditions for 5.0 g of chicken-feathers moistened with distilled water (1:1, w/v, adjusted to pH 8.0) supplemented with maltose (10%, w/w) and sodium nitrate (1.25%, w/w) as best co-carbon and co-nitrogen sources, respectively resulted in 5-fold increase of β-keratinase production post-72 h of incubation at 50 °C compared to β-keratinase production under un-optimized condition. The purified β-keratinase was a 20.1 kDa molecular weight serine protease requiring Fe2+ for enzyme activity, showed restricted substrate specificity for β-keratin, and exhibited a significant stability and compatibility with surfactants, and most of the tested commercial laundry detergents, thus demonstrating its feasibility for inclusion in laundry detergents formulations.